实现静音按钮时应用崩溃

Question

>我编程了一个测验，现在我在 FOR 查询下设置了一个媒体播放器，每次用户点击正确答案时都会播放声音。现在在同一个活动中，我希望 bttOFF 将活动的声音静音，我该怎么做？我用 mp.setVolume(0,0( 设置了一个 onClickListener;但是应用程序在重新启动时崩溃。感谢您的观看！:D

public class QuizActivity extends AppCompatActivity {
private ActionBarDrawerToggle mToggle;
private QuestionLibrary mQuestionLibrary = new QuestionLibrary();
private TextView mScoreView;
private TextView mQuestionView;
private Button mButtonChoice1;
private Button mButtonChoice2;
private Button mButtonChoice3;
private String mAnswer;
private int mScore = 0;
private int mQuestionNumber = 0;
Dialog dialog;
Dialog dialog2;
TextView closeButton;
TextView closeButton2;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_quiz);
final MediaPlayer mp = new MediaPlayer();
//Dialog 1
createDialog();
Button dialogButton = (Button) findViewById(R.id.dialogbtn);
dialogButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.show();
}
});
closeButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.dismiss();
}
});
//end Dialog 1
//Dialog 2
createDialog2();
Button dialogButton2 = (Button) findViewById(R.id.dialogbtn2);
dialogButton2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog2.show();
}
});

closeButton2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog2.dismiss();
}
});
//end Dialog 2
Button bttON = (Button)findViewById(R.id.bttON);
bttON.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mp.setVolume(0,0);

}

});


TextView shareTextView = (TextView) findViewById(R.id.share);
shareTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent myIntent = new Intent(Intent.ACTION_SEND);
myIntent.setType("text/plain");
myIntent.putExtra(Intent.EXTRA_SUBJECT, "Hello!");
myIntent.putExtra(Intent.EXTRA_TEXT, "My highscore in Quizzi is very high! I bet you can't beat me except you are cleverer than me. Download the app now! https://play.google.com/store/apps/details?id=amapps.impossiblequiz");
startActivity(Intent.createChooser(myIntent, "Share with:"));
}
});
mQuestionLibrary.shuffle();

setSupportActionBar((Toolbar) findViewById(R.id.nav_action));
DrawerLayout mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
mToggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
getSupportActionBar().setDisplayHomeAsUpEnabled(true); // Able to see the Navigation Burger "Button"
((NavigationView) findViewById(R.id.nv1)).setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.nav_stats:
startActivity(new Intent(QuizActivity.this, Menu2.class));
break;
case R.id.nav_about:
startActivity(new Intent(QuizActivity.this, Menu3.class));
break;
}
return true;
}
});
mScoreView = (TextView) findViewById(R.id.score_score);
mQuestionView = (TextView) findViewById(R.id.question);
mButtonChoice1 = (Button) findViewById(R.id.choice1);
mButtonChoice2 = (Button) findViewById(R.id.choice2);
mButtonChoice3 = (Button) findViewById(R.id.choice3);
final List<Button> choices = new ArrayList<>();
choices.add(mButtonChoice1);
choices.add(mButtonChoice2);
choices.add(mButtonChoice3);
updateQuestion();

for (final Button choice : choices) {
choice.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (choice.getText().equals(mAnswer)) {

try {
mp.reset();
AssetFileDescriptor afd;
afd = getAssets().openFd("sample.mp3");
mp.setDataSource(afd.getFileDescriptor(),afd.getStartOffset(),afd.getLength());
mp.prepare();
mp.start();
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
updateScore();
updateQuestion();
Toast.makeText(QuizActivity.this, "Correct", Toast.LENGTH_SHORT).show();

} else {
Toast.makeText(QuizActivity.this, "Wrong... Try again!", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(QuizActivity.this, Menu2.class);
intent.putExtra("score", mScore); // pass score to Menu2
startActivity(intent);
}
}
});
}
}
private void updateQuestion() {
if (mQuestionNumber < mQuestionLibrary.getLength()) {
mQuestionView.setText(mQuestionLibrary.getQuestion(mQuestionNumber));
mButtonChoice1.setText(mQuestionLibrary.getChoice1(mQuestionNumber));
mButtonChoice2.setText(mQuestionLibrary.getChoice2(mQuestionNumber));
mButtonChoice3.setText(mQuestionLibrary.getChoice3(mQuestionNumber));
mAnswer = mQuestionLibrary.getCorrectAnswer(mQuestionNumber++);
} else {
Toast.makeText(QuizActivity.this, "Last Question! You are very intelligent!", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(QuizActivity.this, Menu2.class);
intent.putExtra("score", mScore);
startActivity(intent);
}
}
private void updateScore() {
mScoreView.setText(String.valueOf(++mScore));
SharedPreferences mypref = getPreferences(MODE_PRIVATE);
int highScore = mypref.getInt("highScore", 0);
if (mScore > highScore) {
SharedPreferences.Editor editor = mypref.edit();
editor.putInt("highScore", mScore);
editor.apply();
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
return mToggle.onOptionsItemSelected(item) || super.onOptionsItemSelected(item);
}
private void createDialog() {
dialog = new Dialog(this);
dialog.setTitle("Tutorial");
dialog.setContentView(R.layout.popup_menu1_1);
closeButton = (TextView) dialog.findViewById(R.id.closeTXT);
}

private void createDialog2() {
dialog2 = new Dialog(this);
dialog2.setTitle("Settings");
dialog2.setContentView(R.layout.popup_menu1_2);
closeButton2 = (TextView) dialog2.findViewById(R.id.closeTXT2);
}

日志猫：

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at shapy.appz.QuizActivity.onCreate(QuizActivity.java:96)

Answer 1

你可以从你的closeButton和closeButton2findViewById

Answer 2

如 MediaPlayer 类的文档所示 [这里]( https://developer.android.com/reference/android/media/MediaPlayer.html#setVolume(float， float( ( 所需的参数是浮点数。您可以尝试这样做：

public void onClick(View v) {
mp.setVolume( 0.0, 0.0 );
}

看看这是否能解决你的问题。

设置卷

在 API 级别 1 中添加

void setVolume (float leftVolume, float rightVolume)

设置此播放器的音量。建议使用此 API 来平衡应用程序中音频流的输出。除非您正在编写应用程序来控制用户设置，否则应优先使用此 APIsetStreamVolume(int, int, int)，后者设置特定类型的所有流的音量。请注意，传递的卷值是 0.0 到 1.0 范围内的原始标量。UI 控件应按对数缩放。

参数

leftVolume  float: left volume scalar
rightVolume float: right volume scalar